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FDG PET/CT in carcinoma of unknown primary.

Kwee TC, Basu S, Cheng G, Alavi A - Eur. J. Nucl. Med. Mol. Imaging (2009)

Bottom Line: Carcinoma of unknown primary (CUP) is a heterogeneous group of metastatic malignancies in which a primary tumor could not be detected despite thorough diagnostic evaluation.Because of its high sensitivity for the detection of lesions, combined (18)F-fluoro-2-deoxyglucose positron emission tomography (FDG PET)/computed tomography (CT) may be an excellent alternative to CT alone and conventional magnetic resonance imaging in detecting the unknown primary tumor.This article will review the use, diagnostic performance, and utility of FDG PET/CT in CUP and will discuss challenges and future considerations in the diagnostic management of CUP.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands. thomaskwee@gmail.com

ABSTRACT
Carcinoma of unknown primary (CUP) is a heterogeneous group of metastatic malignancies in which a primary tumor could not be detected despite thorough diagnostic evaluation. Because of its high sensitivity for the detection of lesions, combined (18)F-fluoro-2-deoxyglucose positron emission tomography (FDG PET)/computed tomography (CT) may be an excellent alternative to CT alone and conventional magnetic resonance imaging in detecting the unknown primary tumor. This article will review the use, diagnostic performance, and utility of FDG PET/CT in CUP and will discuss challenges and future considerations in the diagnostic management of CUP.

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FDG PET/CT in a 61-year-old woman who presented with a right neck mass. Neck CT confirmed the pathologically enlarged right cervical lymph node, showed slight asymmetry at the right tongue base and oropharynx, and an enlarged, heterogeneous right lobe of the thyroid gland. Fine-needle biopsy and subsequent histopathological examination of the pathologically enlarged right cervical lymph node indicated metastatic carcinoma of unknown primary. Tumor cells were positive for CK7, focally positive for TFF1, and negative for calcitonin and thyroglobulin, suggesting the possibility of a primary lung tumor. FDG PET in the axial (a) and coronal plane (d) shows intense FDG uptake of the thyroid (arrows), likely representing the primary tumor, and intense FDG uptake in the right cervical, supraclavicular, and paratracheal lymph nodes. Corresponding CT and fused FDG PET/CT images in the axial (b, c, respectively) and coronal plane (e, f, respectively) confirm the localization of the lesions seen at FDG PET (arrows). Fine-needle aspiration of the thyroid and subsequent histopathological examination revealed a primary papillary thyroid carcinoma
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Fig2: FDG PET/CT in a 61-year-old woman who presented with a right neck mass. Neck CT confirmed the pathologically enlarged right cervical lymph node, showed slight asymmetry at the right tongue base and oropharynx, and an enlarged, heterogeneous right lobe of the thyroid gland. Fine-needle biopsy and subsequent histopathological examination of the pathologically enlarged right cervical lymph node indicated metastatic carcinoma of unknown primary. Tumor cells were positive for CK7, focally positive for TFF1, and negative for calcitonin and thyroglobulin, suggesting the possibility of a primary lung tumor. FDG PET in the axial (a) and coronal plane (d) shows intense FDG uptake of the thyroid (arrows), likely representing the primary tumor, and intense FDG uptake in the right cervical, supraclavicular, and paratracheal lymph nodes. Corresponding CT and fused FDG PET/CT images in the axial (b, c, respectively) and coronal plane (e, f, respectively) confirm the localization of the lesions seen at FDG PET (arrows). Fine-needle aspiration of the thyroid and subsequent histopathological examination revealed a primary papillary thyroid carcinoma

Mentions: Finally, special attention should be paid to the evaluation of the oropharynx and lung, because these are the locations with the most frequently reported false-positive FDG PET/CT results [12] (Figs. 1 and 2). The oropharynx is a difficult area to evaluate; physiological FDG uptake in the lymphoid tissue of the adenoids and Waldeyer’s ring, and overlap between tumor and physiologic FDG uptake, may impair diagnostic performance [24]. Nevertheless, accurate localization of increased FDG uptake using CT images may, in part, reduce the rate of false-positive results (e.g., recognition of physiological muscle FDG uptake). Furthermore, although focally increased FDG uptake may resemble a primary lung cancer, its CT pattern may indicate the presence of a benign inflammatory or infectious lesion (e.g., pneumonias usually present with a lobular, segmental, or lobar pattern on CT), or a pulmonary embolism or infarction (e.g., a wedge-shaped peripheral region of consolidation on CT should raise the possibility of a pulmonary infarction) [25–27].


FDG PET/CT in carcinoma of unknown primary.

Kwee TC, Basu S, Cheng G, Alavi A - Eur. J. Nucl. Med. Mol. Imaging (2009)

FDG PET/CT in a 61-year-old woman who presented with a right neck mass. Neck CT confirmed the pathologically enlarged right cervical lymph node, showed slight asymmetry at the right tongue base and oropharynx, and an enlarged, heterogeneous right lobe of the thyroid gland. Fine-needle biopsy and subsequent histopathological examination of the pathologically enlarged right cervical lymph node indicated metastatic carcinoma of unknown primary. Tumor cells were positive for CK7, focally positive for TFF1, and negative for calcitonin and thyroglobulin, suggesting the possibility of a primary lung tumor. FDG PET in the axial (a) and coronal plane (d) shows intense FDG uptake of the thyroid (arrows), likely representing the primary tumor, and intense FDG uptake in the right cervical, supraclavicular, and paratracheal lymph nodes. Corresponding CT and fused FDG PET/CT images in the axial (b, c, respectively) and coronal plane (e, f, respectively) confirm the localization of the lesions seen at FDG PET (arrows). Fine-needle aspiration of the thyroid and subsequent histopathological examination revealed a primary papillary thyroid carcinoma
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2822231&req=5

Fig2: FDG PET/CT in a 61-year-old woman who presented with a right neck mass. Neck CT confirmed the pathologically enlarged right cervical lymph node, showed slight asymmetry at the right tongue base and oropharynx, and an enlarged, heterogeneous right lobe of the thyroid gland. Fine-needle biopsy and subsequent histopathological examination of the pathologically enlarged right cervical lymph node indicated metastatic carcinoma of unknown primary. Tumor cells were positive for CK7, focally positive for TFF1, and negative for calcitonin and thyroglobulin, suggesting the possibility of a primary lung tumor. FDG PET in the axial (a) and coronal plane (d) shows intense FDG uptake of the thyroid (arrows), likely representing the primary tumor, and intense FDG uptake in the right cervical, supraclavicular, and paratracheal lymph nodes. Corresponding CT and fused FDG PET/CT images in the axial (b, c, respectively) and coronal plane (e, f, respectively) confirm the localization of the lesions seen at FDG PET (arrows). Fine-needle aspiration of the thyroid and subsequent histopathological examination revealed a primary papillary thyroid carcinoma
Mentions: Finally, special attention should be paid to the evaluation of the oropharynx and lung, because these are the locations with the most frequently reported false-positive FDG PET/CT results [12] (Figs. 1 and 2). The oropharynx is a difficult area to evaluate; physiological FDG uptake in the lymphoid tissue of the adenoids and Waldeyer’s ring, and overlap between tumor and physiologic FDG uptake, may impair diagnostic performance [24]. Nevertheless, accurate localization of increased FDG uptake using CT images may, in part, reduce the rate of false-positive results (e.g., recognition of physiological muscle FDG uptake). Furthermore, although focally increased FDG uptake may resemble a primary lung cancer, its CT pattern may indicate the presence of a benign inflammatory or infectious lesion (e.g., pneumonias usually present with a lobular, segmental, or lobar pattern on CT), or a pulmonary embolism or infarction (e.g., a wedge-shaped peripheral region of consolidation on CT should raise the possibility of a pulmonary infarction) [25–27].

Bottom Line: Carcinoma of unknown primary (CUP) is a heterogeneous group of metastatic malignancies in which a primary tumor could not be detected despite thorough diagnostic evaluation.Because of its high sensitivity for the detection of lesions, combined (18)F-fluoro-2-deoxyglucose positron emission tomography (FDG PET)/computed tomography (CT) may be an excellent alternative to CT alone and conventional magnetic resonance imaging in detecting the unknown primary tumor.This article will review the use, diagnostic performance, and utility of FDG PET/CT in CUP and will discuss challenges and future considerations in the diagnostic management of CUP.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands. thomaskwee@gmail.com

ABSTRACT
Carcinoma of unknown primary (CUP) is a heterogeneous group of metastatic malignancies in which a primary tumor could not be detected despite thorough diagnostic evaluation. Because of its high sensitivity for the detection of lesions, combined (18)F-fluoro-2-deoxyglucose positron emission tomography (FDG PET)/computed tomography (CT) may be an excellent alternative to CT alone and conventional magnetic resonance imaging in detecting the unknown primary tumor. This article will review the use, diagnostic performance, and utility of FDG PET/CT in CUP and will discuss challenges and future considerations in the diagnostic management of CUP.

Show MeSH
Related in: MedlinePlus